Four papers · Different kinds of connection
What crosses the paper boundary?
The same constants, the same counting arguments and the same light pulse turn up in more than one of the four papers. The map says which kind of connection each one is, from a premise one paper borrows from another to a link physicists drew decades later. The first is evidence of how the papers depend on each other; the last is a resemblance.
Uses a result
The energy transformation that leaves the relativity paper
Relativity §8 supplies the light-energy transformation used in the September paper. The two opposite emissions can have unequal energies in a moving frame; comparing the two body-energy ledgers removes unknown internal energies. The quantum hypothesis is not needed for this step.
Relativity §8 · Finite light complex · Mass–energy paper · Two energy ledgers
Takes a premise
The foundations the September paper says it laid down in June
The mass–energy paper’s first footnote is the relativity paper: “A. Einstein, Ann. d. Phys. 17. p. 891. 1905.” Its second paragraph says what it takes from there: “There I took as a basis the Maxwell-Hertz equations for empty space, together with Maxwell’s expression for the electromagnetic energy of space, and in addition the principle:”, and the next paragraph states that principle in full. In the seventh paragraph the principle does its work: “The energy principle must hold for this process, and indeed (by the principle of relativity) with respect to both coordinate systems.” That sentence is where the two energy ledgers get their second coordinate system.
This is the later paper citing the earlier one, so it records which premises the September argument imports. It says nothing about the order in which the two were found, and nothing on this page infers one.
The footnote · What it takes as a basis · The relativity paper’s two postulates · Where the principle is used
Separate routes to one number · Companion preview
What information lets you infer a molecular number?
Compare the radiation-constant calculation with Brownian displacement and a joint viscosity–diffusion inversion. Remove the independent tracer radius to expose what the displacement data cannot identify, or change the viscosity coefficient while holding the observations fixed. Historical reconstruction, illustrative inputs, and modern exact definitions stay visibly distinct.
Shares a mathematical pattern
Counting possibilities without solving every motion
The light-quanta paper compares the volume dependence of dilute radiation entropy with independent configurations. The Brownian paper’s statistical-mechanical argument obtains a volume factor and an osmotic pressure. Independence, logarithms, and volume dependence connect the reasoning; they do not make light and suspended particles the same mechanism.
Light quanta §5 · Independent configurations · Brownian motion §2 · Configuration integral
Later modern synthesis
Light as the instrument
Compare a pulse’s quantum-energy scale, its energy and frequency in another frame, and the system boundary needed to discuss inertia. The interactive light thread keeps the pulse fixed when only the observer changes.
Keep the direction of inference visible
Following a connection never substitutes for reading the argument that supplies it. In particular, using E = hν in a modern comparison is not evidence that the September paper assumed photons, and a simulator that enforces a transformation law is not an experiment testing that law.